tweak header styling

use nabbers, so they are internally consistent
set layout with outerHeight

jQuery changed what `height` means when border-box-sizing is active.  As of jQuery 1.8, `height` *always* means content-height.

[ref](http://blog.jquery.com/2012/08/16/jquery-1-8-box-sizing-width-csswidth-and-outerwidth/)
fix bad `$(body)`